A well-known and very effective extreme pressure additive for lubricating oil is sulfurized sperm oil. The supplies of sperm oil, however, are dwindling in view of whale protection laws. Various materials are being proffered as sperm oil substitutes. One such group of compositions as disclosed in U.S. Pat. No. 3,740,333 are blends of triglycerides and wax esters derived from predominantly C.sub.18-22 unsaturated acids and C.sub.10-16 saturated alcohols; the compositions are disclosed as useful per se and in the sulfurized form. The triglycerides disclosed are those derived from plants and animals and have iodine values between about 50 and 120, with lard oil having an iodine value between about 65 and 80 being a preferred triglyceride.
Lard, a material of low iodine value, may be the equivalent of oils having an iodine value greater than 80, for example, vegetable oils such as rapeseed oil or soya bean oil, in the unsulfurized state; however, upon sulfurization, it has been found that lard oil is not the equivalent of oils having an iodine value greater than 80, e.g., vegetable oils, in that lard oil can be sulfurized to a product having a low viscosity and high solubility in mineral oil. Sulfurization of oils having an iodine value greater than 80 produces a high viscosity, unworkable semi-solid which is only sparingly soluble in hydrocarbon lubricating oils.
The above-mentioned U.S. Pat. No. 3,740,333 discloses that, in the blends of triglyceride and wax ester, alcohols employed to obtain the wax esters are saturated primary alcohols of about 6 to 20 carbon atoms, with best results obtained when the alcohol contains about 10 to 16 carbon atoms. If too low a molecular weight alcohol is used, the resulting blends have high flash points and low viscosities and are less desirable.